This invention relates to an indicator lighting unit for an indicator mounted on a vehicle or the like and, in particular, to an indicator lighting unit which is universally adapted to variation of the layout of an indicator and which is easy in exchange of bulbs.
Generally, a dashboard with various instruments often includes various indicators for making various indications by illumination of lamps. For example, a combination meter mounted on a vehicle such as an automobile comprises major instruments such as a speedometer, a tachometer, a fuel gauge, a water temperature gauge, and a trip odometer. In addition to these major instruments, the combination meter further comprises various warning lamps and pilot lamps as indicators of the type described. These indicators are arranged around the above-mentioned major instruments to indicate operating conditions and abnormal conditions of the automobile by illumination of the lamps.
FIG. 1 shows a combination meter 60 for an automobile. A meter case 62 has a display portion 63. Various instruments 66 such as a speedometer are assembled into the display portion 66. In an automatic car, a shift position indicator 61 and other indicators 64 and 65 are assembled also. In order to provide indications, the shift position indicator 61 and the other indicators 64 and 65 are illuminated by illuminating bulbs which are located on the rear side (backlight).
To arrange the illuminating bulbs in the meter case 62, bulb receiving holes are formed in a rear plate of the meter case 62 to receive the illuminating bulbs. The rear plate is generally provided with a printed circuit board on its inner surface to thereby form an electric circuit. Due to presence of the receiving holes, a sufficient circuit space can not be obtained.
In view of the above, the present applicant proposed a display device for a vehicle (Japanese Utility Model Laid Open No. 4-104743) illustrated in FIG. 2. A combination meter 60 has a meter case 62 in which illuminating bulbs are arranged. An illuminating assembly 70 is formed by a combination of the illuminating bulbs, a circuit board, and a lead wire. The illuminating assembly 70 is removably assembled in the meter case 62 through a window 67 formed in the meter case 62.
In the proposed display unit, the illuminating assembly 70 comprises a display portion 71, a lens 72, a multideck lamp cover 73 with a plurality of cells, a printed circuit board 74, a lead wire 75, and illuminating bulbs 76 as illustrated in FIGS. 3 and 4. The printed circuit board 74 is attached to the lamp cover 73 through screws 77. A receiving portion 73a projects from the bottom of the lamp cover 73. A top plate of the lamp cover 73 is provided with a stopper 73b and an opening 73c for outwardly directing the lead wire 75.
The illuminating assembly 70 is inserted in the meter case 62 through the window 67 formed in the top plate of the meter case 62. The illuminating assembly 70 is properly positioned by bring the receiving portion 73a and the stopper 73b into contact with a guide portion 68 of the meter case 62 and an edge of the window 67, respectively.
With this structure, a printed circuit board can be formed on an outer surface 62a of the meter case 62. A sufficient circuit space is obtained for the printed circuit board because it is unnecessary to provide bulb receiving holes or an electric circuit for the illuminating bulbs 76 on the meter case 62. On the other hand, a plurality of electric circuits for the illuminating bulbs 78 can be formed on the printed circuit board 74 attached to the illuminating assembly 70. The lead wire 75 is drawn out through the opening 78c formed on the top plate of lamp cover 78 of the illuminating assembly 70.
With the display device for a vehicle already proposed by the present applicant, the assembly 70 can be removed from the meter case 62 through the window 62 in order to exchange exhausted one or ones of the illuminating bulbs 76. Thus, efficiency in exchange work is excellent.
However, with the above-mentioned display device for a vehicle, the electric circuit has a route passing through a wire harness, a flexible circuit board, and the bulb. Since a configuration of the meter case is different in dependence upon a type of an automobile, it is necessary to change the shape and the number of the flexible circuit boards. As described, the electric circuit extends over a long distance from the wire harness through the flexible circuit board to the bulb. The layout of the indicator often makes it difficult to design the flexible circuit board.